A liquid crystal display device controls light transmittance of a liquid crystal having dielectric anisotropy by using of an electric field to display a picture. A picture is displayed through a liquid crystal display panel having a liquid crystal cell matrix and a drive circuit for driving the liquid crystal display panel.
The liquid crystal display panel includes a color filter substrate and a thin film transistor substrate which are bonded with a liquid crystal layer therebetween. The color filter substrate includes a black matrix, a color filter and a common electrode sequentially formed on an upper glass substrate. The thin film transistor substrate includes thin film transistors and pixel electrodes formed at cell areas defined by crossing gate lines and data line in a lower glass substrate. The color filter substrate and the thin film transistor substrate can be formed by photolithography, etching, or use of a printing apparatus.
FIGS. 1A to 1C are diagrams depicting a process for printing a target pattern using a printing apparatus of the related art. FIG. 1A depicts a printing apparatus, including a printing roll 3 having a blanket 5 with target pattern forming material 7 spread over the blanket 5 surface. In a first printing step, the printing roll in FIG. 1A is used to print pattern forming material onto printing plate patterns 13 in a printing substrate 11 (FIG. 1B). When the pattern forming material 7 adheres to a printing plate pattern 13 on the printing substrate 11, portions of pattern forming material are removed from the printing roll, thereby creating a target pattern 15 on the surface of the printing roll 3 (FIG. 1B). Then, in a second printing step, the target pattern 15 on the printing roll is printed onto a target substrate 21, thereby creating target pattern 15 thereon (FIG. 1C). A target pattern 15 can be applied as a pattern to various parts of a liquid crystal display device, including the black matrix, color filter, gate line, data line, etc.
A printing plate pattern 13 may be formed using a mask in a photolithography or etching process. FIG. 2 illustrates an etching process for forming a printing plate pattern 13 in which a mask 29 is arranged on the printing substrate 11, exposing an exposure area P2 that can etched to form a desired printing plate pattern 13. Typically, a wet or dry etching method employing a glass substrate as the printing substrate 11 may be used. In view of the disadvantages associated with dry etching, including long process times, high manufacturing costs, and target pattern limitations regarding wide line width, wet etching processes are often preferred.
A fluoric acid solution may be used in a wet etching process. In the isotropic wet etching process depicted in FIG. 2 where the depth of etching is 10 μm, each side of the printing substrate 11 adjacent to the exposure area P2 is also etched by 10 μm. For example, if the exposure area has a line width of 10 μm and the depth of the wet etching is 10 μm, the etched area will have a line width of 30 μm.
When forming a target pattern 15 with a line width of less than 100 μm, the printing plate pattern 13 is normally formed with a height of about 10 μm. However, when forming a target pattern 15 having a line width of 100 μm or more where the height of the printing plate pattern 13 is 10 μm, the target pattern formed in the second printing step may carry an inappropriate separation or break.
FIGS. 3A-3C illustrate a pattern separation problem that can result when etching e.g., a wide line width patterns (e.g., 100 μm or greater) greatly exceeding the height of the printing plate pattern (e.g., 10 μm). In a case where the gap between printing plate patterns 13 is 100 μm or greater and the height of the printing plate pattern 13 is 10 μm, target pattern forming material 7 may inappropriately adhere to the printing substrate 11 between adjacent printing plate patterns 13 (FIGS. 3A, 3B). As a result, a portion of target pattern forming material 7 of width X which is designated for a wide line width target pattern 15 may become inappropriately displaced on the printing substrate 11 (FIG. 3B), so that the resultant target pattern 15 formed in the second printing step carries an inappropriate gap having a width X corresponding to the displaced portion of target pattern forming material (FIG. 3C).
In view of these limitations, related art approaches may utilize one printing substrate to correctly form a target pattern having a wide line width of 100 μm or greater and a second printing substrate to form a target pattern having a wide line width less than 100 μm. Accordingly, there is a need in the art for a fabrication methodology adapted for printing wide line width patterns and narrow wide line width patterns using one printing substrate.